[1] U.S. Pat. No. 5,049,954.
[2] U.S. Pat. No. 5,695,810.
[3] U.S. Pat. No. 6,288,449.
1. Field of the Invention
The present invention relates to a Schottky Structure in a gallium arsenide (GaAs) semiconductor device, particularly to a lower electric resistance and superior heat conductivity with a Schottky Structure. Therefore, this invention can be employed by an easy connective manufacturing process with other manufacturing process for gallium arsenide (GaAs) device.
2. Prior Arts
In General, the Ti/Pt/Au Schottky contact on n-GaAs is the most widely used Schottky structure in the fabrication of metal semiconductor field effect transistors (MESFET), high electron mobility transistors (HEMT) and Schottky diodes. In the Ti/Pt/Au structure, Titanium (Ti) layer provides good Schottky Contract, platinum (Pt) layer acts as a diffusion barrier, and Gold (Au) layer provides high electrical conductivity. Lately, new Schottky structures (Ti/W/Cu, Ti/Co/Cu, Ti/Mo/Cu) with copper and refractory diffusion barrier metal for GaAs semiconductor has become an important device in the field of copper process. A platinum (Pt) layer 32 is replaced with diffusion barrier layer of the refractory material such as tungsten (W), cobalt (Co), tantalum (Ta) and molybdenum (Mo) due to their superior electrical conductivity, lower resistivity and anti-diffusion capability. Gold (Au) layer is replaced with first copper layer due to their lower electric resistance and superior heat conductivity. Thus, it may increase electrical characteristics and it also may do copper process directly.
Kizahi Shimada et al., U.S. Pat. No. 5,049,954, GaAs field effect semiconductor device having Schottky gate structure, which discloses Ti film on a surface of gallium arsenide (GaAs) substrate, and a refractory electrode film on a surface of the Ti film including refractory metals, carbides, and nitrides. But, the present invention provides a first copper layer on a surface of diffusion barrier layer to form a Schottky Structure. Thus, a Schottky Structure which is more useful and of commercial value is obtained.
Valerg M. Dubin et al., U.S. Pat. No. 5,695,810, Use of cobalt tungsten phosphide as a barrier material for copper metallization, which discloses a CoWP barrier material to prevent copper diffusion. But, the present invention provides a diffusion barrier layer on a surface of said titanium (Ti) layer to block metal diffusion.
Siddhartha Bhowmik et al., U.S. Pat. No. 6,288,449, Barrier for copper metallization, which discloses a diffusion barrier layer with multiple layers Ta/TaN/TiN for copper metallization. But, the present invention provides a diffusion barrier layer with a single layer for copper process. Thus, it can be very useful for Schottky Structure.
Therefore, the present invention provides a Schottky Structure in gallium arsenide (GaAs) semiconductor device with copper metallization.
The main object of the present invention is to provide a lower electric resistance and superior heat conductivity with Schottky Structure.
Another object of this invention is to provide a high frequency device with Schottky Structure.
The other object of this invention is to provide an easy connective manufacturing process with Cu metallization process.
The present invention provides a Schottky Structure in gallium arsenide (GaAs) semiconductor device. Please refer to FIG. 1, we disclose a schematic diagram of High Electron Mobility Transistors (HEMT), which comprises a semi-insulating gallium arsenide (GaAs) semiconductor substrate 1, a Schottky structure 2, a copper air bridge 3, air 4, a copper layer 5, a n-type gallium arsenide (n-GaAs) 6, and a nitride 7.
The gold (Au) was replaced with copper due to their lower electric resistance and superior heat conductivity.
Furthermore, the present invention overcomes a deep acceptor problem with copper process. Thus, it can be employed to Monolithic Microwave Integrated Circuit (MMIC). The present invention provides that a new Schottky Structure has excellent characteristic and cost compare to the conventional Ti/Pt/Au structure and can be used as the Schottky Structure for gallium arsenide (GaAs) device